If we take a look to the different kind of aircraft or the different radar devices that were used for the night fighting or the different tactics used, everybody can wonder why so many aircraft, radars and tactics?
The reason is that the night fighting evolved during 1939-1945. Now we are to remark the most important events that took place in the fight that the German had against the British for the control of the Europe sky during the night.
When the first bombing raids by RAF on civilian targets at the beginning of the war, the German night fighting tactics was to seek and destroy the enemy aircraft with no electronic means, but this changed very soon.
Two tactics emerged as the solution to the enemy raids, these ones were named: Dunkel Nachtjagd (dark night fighting) and Helle Nachtjagd (illuminated night fighting).
Dunkel Nachtjagd or DUNAJA (dark night fighting): The fighters were aided by a radio beacon that led them to the targets thanks to Freya stations. When the fighters arrive to the bomber stream, it was needed a visual identification in order to target and shoot the enemy aircraft. In 1940 Freya early warning radars were lined from the Danish to the Swiss frontiers. The first kills were achieved in September 1940.
Helle Nachtjagd or HENAJA (clear or illuminated night fighting): Immediately after the DUNAJA, the Luftwaffe efforts in night fighting were aimed to find a better tactic. Now the pilots were helped by the use of searchlights on the ground (that were controlled by radars too) that illuminated the enemies and at the same time tried to blind the enemy pilots. The searchlight was extended at the beginning from Reims to Flensburg and was divided in 18 zones (each 45 km wide and 35 km deep). It is important remember that the HENAJA stripes of light were Flak-free. The first illuminated zone, or was established near Münster and the first aerial victories using the system were achieved in July 1940 (Oberleutnant Streib). Although the idea was good, the British realized that if they flew around the illuminated zones, they avoided the danger. This one was one of the reasons that made the German effort in the evolution of new techniques involving radar grew.
German Flak only provided a point defense in several areas of the Reich near important targets. The Flak worked together with a radar, an optical range finder and searchlights. Each Flak battery had 4 to 8 guns with calibers of 88 mm, 105 mm or 128 mm. Usually the Flak shells had timers in order to make them explode close to the bombers. The range of the 88 mm and 105 mm shells was 8890 metres; the range of the 128 mm shells was 10927 metres. In 1945 the German Flak had to fire about 10000 shells to shoot down an enemy aircraft. The night fighter had coded signal flares in order to be recognized by the ground defenses.
At the beginning of May 1940 Hauptmann Falck (chief of I./ZG 1) proposed the use of Bf 110s as night fighters after the trials he had done during April 1940.
The increasing British night attacks to the Reich since 1940, showed that at the moment the Luftwaffe has no means enough to stop and destroy the British aircraft marauding the German industries at night. So, on 20th July, Reichmarshall Göring ordered General Kammhuber to set up a night fighter force.
As soon as on 22 June 1940 a new unit of the Luftwaffe was born: the Nachtjagdgeschwader 1 and Falck became its Kommodore. This new unit comprised:
I./NJG 1 with Bf 110.
II./NJG 1 with Ju 88 C-2.
III./NJG 1 with Bf 109.
Most of the night fighter crew were old Zerstörer units crew and flew the Bf 110, that was the main night fighter aircraft in the German arsenal. On 23 July, 1940 the NachtJagddivision HQ was deployed in Brussels and the NJG 1 HQ deployed in Arnhem.
In late 1940, the Germans were developing their own radar system that finally took shape in the FuG 202 Lichtenstein BC, which would be operationally tested in mid-1941. When its utility was demonstrated, it became the standard Luftwaffe airborne radar for the next few years.
Meanwhile the air defense of the Reich was improving, another tactic was developed by the Luftwaffe against the British bombers: the “Fernnachtjagd”. This tactic was based in long range missions conducted by German night fighters over enemy controlled territory to attack the enemy bombers during their return home route after bombing and when near of their airfields. The idea was easy, night fighters missions over enemy territory to harass the British bomber fleet or indeed attack ground targets in enemy airfields with long range night intruders as the Ju 88 C (C-1 and C-2) and Do 17 Z-7 and Z-10 at the beginning belonging to II./NJG 1 (this unit on September 11, 1940 was renamed I./NJG 2) based at Gilze-Rijen in Netherlands. In the spring of 1941 several Do 215 B-5 carried out “Fernnachtjagd” missions. The British bombers were vulnerable when taking off and when assembly, and that opportunity and the German night fighters took advantage of it.
The “Fernnachtjagd” was a success because many enemy bombers were shot down, mainly during January to early October 1941, but on October 12, 1941 a Hitler´s order was received: stop immediately all the “Fernnachtjagd” missions. The main reason was that enemy bombers continued their attacks despite the “Fernnachtjagd” missions.
We have to remark that Germany took the first steps for the modern night fighting with the Spanner-Gerät infrared detection system. It consisted in an IF searchlight and a monitor display that could enable the pilot to illuminate with the infrared light the enemy bomber in the dark of the night then locate it in the monitor; but it never worked well because it received too many signals that confused the pilot.
Although after 1941, the Helle Nachtjagd was abandoned slowly in favor of the “combined” fighting zone, both Dunkel Nachtjagd and Helle Nachtjagd continued, but several important improvements were achieved in the night fighting.
For example, the HENAJA was aided with the arriving of the new Würzburg radar, which had the precision to direct a searchlight beam onto a bomber. The DUNAJA was improved thanks to the “‘Giant” Würzburg (Würzburg-Riese) that complemented the Freya radar.
Thanks to the higher experience in both tactics, about the spring of 1942 it´s considered that the German night fighting system began to work effectively.
But when everything was more controlled, the Hitler’s orders to gradually withdrawn the searchlight belt from March to July 1942 to reinforce the main cities defense. So, the HENAJA had to change to a “combined” fighting zone (named KONAJA) that tried to combine Flak, the searchlights and fighters over several target cities.
It was very important for the KONAJA that the Flak fired only below 4000 meters and the night fighters always had to fly over this height to avoid any surprise from their own artillery. The risk when flying into the Flak zone always was present when the night fighter pursued the enemy aircraft.
The withdrawing of the searchlights motived that emerged a new night fighting method, the Himmelbett (Four Post Bed). It consisted in a line of radar stations about 30 km apart one from another completed with Flak (AAA) and searchlights. Every radar station was equipped with a Freya (160 km range) and 2 Würzburg radars (65 km range). So, the Freya had to locate the enemy aircraft as early warning and the two Würzburg (“Red Giant” Würzburg-Riese and “Green Giant” Würzburg-Riese) tracked a night fighter and guided it towards the enemy aircraft (measuring altitude, numbers and direction). When the position of the bomber and the night fighter were known these ones were transmitted to a Seeburg plotting table (on wich positions of friend or foe aircraft were displayed) from which a controller would guide the pilot in order to intercept the bomber. The night fighters had to be assigned to defined zones where they had to fly while waiting orders from ground control. It was necessary that always the aircraft were flying circling over a radio beacon in the waiting area, because the time to intercept the enemy aircraft was very little. One important limitation of the Himmelbett system was that each ground control station only has capability to manage to guide one night fighter against one enemy aircraft at any one time in each zone (while one night fighter was flying, a second aircraft was on ground ready to take off and the third one was held in reserve).
The creator of the Himmelbett, Josef Kammhuber (the head of the German night fighters) achieved to build a line of ground-controlled night-fighting zones from France to Denmark in the so called Himmelbett system and nicknamed the Kammhuber Line.
The importance of the night fighting was showed when during 1942 were activated two new units: NJG 4 and NJG 5.
Another important point was the deployment of FuG 202 Lichtenstein B/C AI radar (with 32 di-pole antennas) aboard aircraft in mid-1942. Thanks to the radar fitted in the night fighters, the pilots could get terminal guidance to the bombers because its limited range. With the arriving of the airborne radars, the German night fighters gained air superiority in many cases. But many pilots preferred to maintain the performance of the night fighter better than increase the drag of the aircraft because the antenna arrangement, and continue being guided to the bombers stream from the ground.
The first enemy aircraft shot down thanks to the Lichtenstein AI radar took place on the night of 9 August 1941, and the pilot was Ludwig Becker. That night the “modern” night fighting was born. Despite the improving in the German night fighters, the chances to shoot down a bomber at night, remained elusive because until 1942 RAF’s Bomber Command had been sending bombers over Germany in small formations. And the RAF losses were running at an unacceptable rate of almost 7% due to the DUNAJA and Himmelbett systems. But the arrival of Air Marshal Sir Arthur Harris in late February 1942 marked significant changes in RAF tactics. From that moment massive bomber formations were concentrated in narrow section of the defensive line in the shortest period of time, collapsing the German defensive system. The higher concentration of bombers, the lower the losses. So, the loss rate changed to 3.9% with the new RAF tactic.
From March 1942 the British were using several electronic devices to help them in their missions: a navigational aid named GEE that only could range out over the Ruhr, the Oboe that guided the bomber and showed the place where drop the bombs. Another device was the H2S, that was used since January 1943. The H2S was a downward-looking radar that could identify cities based in the shape (with longer range than the Oboe, the H2S allowed a blind bombing over the targets). Thanks to the Oboe and H2S, the British bombings improving very much.
During September 1942, British Bomber Command lost 212 aircraft, about the 40% of its bomber inventory: and during 1942 the German night fighters claimed more than 800 British aircraft shot down, and many of them thanks to the use of radar equipped night fighters. The Bf 110 F and G were the main night fighter used by the NJGs. While the enemy aircraft in the skies of the Reich were increasing, the night fighter force continued to expand with new NJGs. Besides, the combat experience of the German night fighter pilots allowed an improved training.
When American bombers joined to British ones in the non stop campaign of bombing the Reich (British in night missions and American in daytime missions), the German night fighters had to do their best.
From March to July 1943, the British kept the named Battle of the Ruhr (this area was in the range of the Oboe devices) and destroyed many German factories concentrated in the area. The British launched 43 attacks over the Ruhr area, destroying their targets but their losses were about 4.7%.
Also the German night fighters flew missions over the Atlantic ocean from ther French bases because a IV./NJG 5 detachment was sent to the Western French coast.
Although the German night fighting was mature in 1943 thanks to General Kammhuber, very soon the German night force received a new strike that almost paralysed it: the “Window” (known as Düppeln in German). They were metallic (aluminium) foil strips one half-wavelength in length that would create a significant radar echo on a scope, confusing and jamming the German radars and therefore the control of searchlights, Flak and night fighters (so the DUNAJA defensive system became almost useless). It was capable of jamming the FuG 202, FuG 212 and the Würzburg ground radars. This new secret weapon was developed by the Allies and was ready in mid-1942 but Window was used the first time on the night of 24/25 July 1943 during the Operation Gomorrah against the city of Hamburg. From that day, the Window was used in many raids against German cities almost blinding the German night force because the ground controllers could not guide the night fighters towards the enemy. Fortunately for the Luftwaffe, very shortly before the Window appeared over Germany, a new night fighter tactic was developed by Major Hajo Herrmann: the “Wilde Sau” (Wild Boar).
In the “Wilde Sau”, single-seat fighters (Fw 190 and Bf 109) could take advantage of the anti-aircraft artillery (AAA or Flak) that was posted close to the searchlight system (and preferably above the altitude of the British bombers). The fighters “only” had to stay above the altitude at which AA grenades would explode while the searchlights tracked the bombers stream and picked up targets. This tactic was better if the searchlights illuminated the lower cloud layer. The bombers were easier to detect against illuminated clouds or thanks to the torches that could be shot by the AAA to increase the illumination (although the bomber stream never was easy to track). At that moment, the fighters could see the enemies and attack them. As a positive point, the radar was not necessary, so the Window didn´t affected these single-seat nigh fighters. In the negative side, to fly in the dark of the night without ant radar was very dangerous.
This tactic had an important problem because the pilots were before day fighter pilots that were mostly inexperienced in instrumental flying. This was the reason of a lot of accidents when landing or during take off. In this case, the Bf 109 was the favourite because without visibility the accidents were more dangerous in an aircraft with a wide landing gear as the Fw 190.
Although “Wilde Sau” tactics were used, still during the shock that Window has caused in the night fighter force, a new tactic was developed by Oberst von Lossberg: “Zahme Sau” (Tame Boar). This time it was needed to linking the German radar stations and the fitting of a new and improved radar aboard the aircraft that was not affected by Window. The tracking of the stream bomber was not as precise as before but the ground controller could send several night fighters in the right direction to infiltrate the RAF bomber streams (the addition of passive receivers in the night fighters aided greatly in leading them to their targets). Once the night fighters were near the bombers, they could track them with the radar.
On 1 August 1943, the 5 “Jagddivisionen” of the XII Fliegerkorps commanded by General der Flieger Kammhuber were:
1. Jagddivision: I, II, III and IV./NJG 1. Commanded by Generalmajor von Döring.
2. Jagddivision: I, II, III and IV./NJG 3 and Nachjagdkommando 190. Commanded by Generalleutnant Schwabedissen.
3. Jagddivision: II./NJG 4. Commanded by Generalmajor Junck.
4. Jagddivision: I and III./NJG 4, I and II./NJG 2, I, II and III./NJG 5. Commanded by Generalmajor Huth.
5. Jagddivision: I./NJG 6. Commanded by Oberst von Bülow.
The night 18/19 November 1943 began the “Battle of Berlin”, an Allied bombing campaign designed to destroy Berlin taking advantage of the “Window” effect on the night fighter force performance. The GEE and Oboe devices worked fine, but the H2S did not work well in the range of Berlin. There were 35 raids against the Berlin area with British losses near the 10% (more than a rate of 5% was considered unacceptable for the British Bomber Command). So the Battle of Berlin was considered as a German victory.
So, at the end of 1943, “Zahme Sau”, “Wide Sau” and Himmelbett systems coexisted trying to stop the British raids. From that time, another war between the RAF and Luftwaffe was fought, but this one the war was across the radio spectrum. But despite all the German efforts and the more intensive training of the new night fighter crews in infiltration methods against the bomber streams: these counter measurements didn’t achieve to stop the bombing and destruction of Germany.
Against the night fighting principles, but due to the American bombers that started to fill the German skies, sometimes the night fighters were required to fly as day fighters. In day missions, the night fighters sometimes were armed with with four 21 cm diameter rockets (in the Bf 110 for example) that reduced the performance and handling of the aircraft very considerably. The results were a disaster because the aircraft and pilots had little chance to survive in combat against the bombers and their escort fighter. Also the Bomber Command 100 Group was formed in November 1943 with a task: electronic countermeasures against the German radars system (the propose was to avoid the detection of the approaching bomber stream); and the Mosquito night fighters started their marauding missions over the Reich (the German night fighters could hardly do anything against the faster Mosquitoes; and this was one of the reasons of the change of the Bf 110 for the faster Ju 88 as the backbone of the NJGs). Jamming escorts were together the bomber stream in order to jam the German communications and navigation aids. Since November 1943, the Luftwaffe knew about this new British Group and its task. The British bomber formations were aided by the pathfinders, they were aircraft that flew ahead of the main forces and marked the targets with flares; and the pathfinder role was played usually for Mosquitoes.
The Mosquitoes in bomber, reconnaissance and night fighter versions were a constant worry for the German night fighter force. Sometimes the Mosquito night fighters set up ambushes to night fighter beacons and airfields to harass the German defenders.
Against the Mosquitoes some Bf 109 G-5 were fitted to fight the British twin engine aircraft. These Bf 109s were deployed in the JG 300 and JG 302, and had mounted a DB 605AS engine with turbocompressor. Also, the Bf 109 G-5s had reduced weight and armament (only one cannon and two machine guns) in order to catch the Mosquito.
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